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Small amps, big power

JL Audio's HD Series amplifiers offer high performance from an ultra-compact chassis. These Class D amplifiers use less power, take up less space, and generate less heat than traditional amp designs — you can even stack them up to create a sweet-looking installation.

JL Audio technology goes to work for you

HD Series amplifiers reproduce your music with exceptional accuracy, so you'll hear high-fidelity sound even under the most demanding conditions. JL Audio uses Single Cycle Control™ technology to eliminate the excessive signal distortion that's plagued Class D amplifiers in the past. Differential-balanced inputs eliminate noise before it hits the preamp stage, and allow you to connect the amp to just about any in-dash stereo. You'll hear clear, true, studio-quality audio, exactly what you expect from JL Audio.

Power your entire system with one compact amp

The 5-channel HD900/5 amplifier pushes 100 watts RMS per channel to your front and rear full-range speakers, plus 500 watts RMS to a sub — all from a 2" tall chassis that's about the size of a sheet of computer paper. Or, you can bridge the front and rear channels to drive 150 watts RMS into two speakers, while still running your sub at 500 watts.

The regulated power supply allows this amp to deliver its rated power to a wide range of impedances, even when voltage levels drop during heavy use. Removable power and speaker plugs make it easy to pop this amp out if you need the space in your cargo area.

Some extra touches

You can use JL Audio's optional stack kit to mount one HD Series amp on top of another, so you can maximum power from minimum space. JL's wired remote allows you to control your HD amp's volume from your front seat.

My system has plenty of power. Who needs an amp?

You might think you don't need an amp because you have a 400-watt system in your car, or because your new stereo puts out 50 watts a channel. But those are peak wattage ratings, which may boil down to 15 or 20 watts per channel, using the more realistic RMS rating. An amp sends your speakers the power they need to deliver your music with clarity and impact, whether you're using factory speakers or high-performance components. And low-frequency reproduction requires lots of power, so an amp is an absolute must if you're adding a sub to your system.

Product Research

Features

Five-Channel Full-Range Amplifier: The JL Audio HD900/5 is a
Class D five-channel, full-range amplifier that is rated at 75 to 100 Watts RMS x 4-channel
(front/rear) and 500 Watts x 1-channel (subwoofer) in 1.5-4-ohm at 20 to 20kHz
with a signal-to-noise-ratio of 108 dB and a total
harmonic distortion of 0.03% while receiving 11 to14.5 Volts. The front and rear
channels of the amplifier can
also be bridged to output 150-200 Watts RMS x 2-channel in 3 to 8-ohms.

High-Fidelity Class D (HD) With Single-Cycle Control: The JL Audio HD900/5 utilizes patented Single Cycle Control Class D technology
for all channels. This technology delivers reference-grade sonic performance
while requiring far less current from the vehicle's electrical systems than a
conventional amplifier. Single Cycle Control is a unique approach to
controlling a full-range Class D amplifier. By tracking the audio signal,
comparing it to the real PWM waveform and then correcting it in each and every
cycle (over 400,000 times per second), a multitude of distortion-causing
mechanisms can be tightly controlled to enable pristine amplification.
While there are certainly less expensive ways to make a full-range switching
amplifier, no other Class D control system works faster or more accurately than
Single Cycle Control.

Compact/Efficient Design: The JL Audio Class D amplifier on average is
13% smaller overall and over 1/2-inch shorter in height than most class AB
amplifiers. The HD900/5 features outstanding overall efficiency (80% at 1/2
rated power) which allows for huge power from a tiny chassis and is easy on your
vehicle's charging system, drawing 60% less current than a class AB design of
equal power.

R.I.P.S. (Regulated, Intelligent Power Supply): R.I.P.S. stands for
"Regulated, Intelligent Power Supply" and is a central feature of the JL Audio's
JL Audio HD amplifier. The JL Audio R.I.P.S. System ensures consistent power
delivery over a wide range of battery voltages and load impedances. This
technology provides optimum power at any impedance level between 1.5 ohm to 4
ohm per channel and at any vehicle voltage level between 11V and 14.5V.

Regulated Power Supply: "Regulated" means that the power supply
adjusts its operation so as to maintain the amplifier's rated power output
and low distortion operation over a wide range of vehicle voltages (11V-14.5
V). This allows the JL Audio JL Audio HD amplifier's the rail voltage and clean
power output to remain stable in real-world car-audio systems, resulting in
superior fidelity and stability.

Intelligent Power Supply: The "Intelligent" portion of the
R.I.P.S. System is a circuit that actually monitors output current to
optimize the amplifier's output power over a wide range of load impedances
(1.5 ohm to 4 ohm per channel). The R.I.P.S. System detects the actual
impedance being driven and adjusts output rail voltages to deliver optimum
output. The entire process is seamless, automatic, and results in incredible
dynamics for satellite channels and consistent power output for a wide range
of subwoofer configurations. It also takes into account the real impedance
of your car-audio system, rather than relying on often inaccurate
assumptions based on a speaker's rated impedance.

RealSink Heat Management With Rollback Protection:
This JL Audio amplifier employ and advanced type of heat management, called RealSink. This features takes advantage of
convection and radiation effects to remove heat from the amplifier circuitry.
For optimum cool performance, the vertical heat sinks located at the sides of
the amplifier should be exposed to as large a volume of air as possible. If a JL Audio HD amplifier should ever reach an unsafe temperature, its unique Advanced Rollback Protection circuit also adjusts power until the amplifier
cools down, without ever shutting your music down.

Differential-Balanced Inputs: The JL Audio amplifier features
differential-balanced input architecture to effectively control noise and ensure
compatibility with a wide variety of source units, including many OEM
systems. Without resorting to line output converters, you can directly connect
most OEM source units to the JL Audio amplifier without creating any noise or
compatibility issues. Unlike conventional single-ended inputs, the
differential-balanced design does not connect one side of the audio signal to
chassis ground. This eliminates any voltage sensitivity between one input
terminal and ground and greatly reduces the incidence of alternator whine in a
typical car audio installation. The JL Audio HD amplifier provides range switching
on each of its inputs via the "Input Voltage" switch. This permits connection to
a wide range of source voltages while retaining excellent sensitivity setting
precision.

Note: You will need three speaker wire to RCA adaptors (136XDCLR2S,
sold separately) to connect this amplifier to your headunit via
speaker-level.

Protection Circuitry With Status Indicator Lights: There is
a single multi-color LED on the control panel of the amplifier to indicate the amplifier's operating status.

Flashing Green: When
the LED is flashing green, the amplifier is powering up and audio output is
muted.

Constant Green: This LED lights green to indicate that the
amplifier is turned on and operating normally.

Constant Red: This Red LED lights to indicate that the amplifier
has exceeded its safe operating temperature, putting the amplifier into a
shelf-protection mode, which reduces the power output of the amplifier. The
red light will shut off and the amplifier will return to normal, full-power
operating mode if the heat sink temperature drops back to a safe level.

Constant Yellow: This amber LED lights to indicate that the
impedance of the speaker load connected to the amplifier is lower than the
optimum impedance load range for the amplifier. When this light is on, a
protection circuit engages and reduces the power output of the amplifier.
The amber indicator will also light when a short-circuit is detected in the
speaker wiring.

Alternating Red/Green: The LED alternated between Red and Green to
indicate that the amplifier is experiencing a fault that may require service
of the amplifier, its wiring, or the vehicle's operating system. Audio is
muted when this fault occurs.

Note: There is only one condition that will shut down the
HD900/5 completely and that is if the battery voltage of your vehicle
drops below 10 volts.

Mounting Options: The HD900/5 has two mounting option to choose from
during installation.

Standard Mounting: The standard method of mounting
requires removal of the four corner caps with the included hex-wrench. Using the appropriate mounting screws (not included), you can
then secure the amplifier in all four corners and replace the corner caps.

Lateral Mounting Feet: Lateral Mounting Feet are also included
with the HD900/5 to provide an alternative mounting option. Each mounting
foot should be attached to the bottom of the amplifier by screwing the
provided bolts into the bottom of the amplifier and up into the corner cap
with the supplied hex-wrench. Then, using the appropriate
mounting screws (not included), you can secure the amplifier by its four
lateral mounting feet.

Controls

Control Panel Cover: The
HD900/5 features a Control Panel Security Cover which protects and hides the
amplifier's controls. When installed, the cover ensures that the amplifier's
settings are not accidentally changed while creating a clean aesthetic look for
the amplifier and your installation. The control panel security cover is
pre-installed at the factory and must be temporarily removed for access the
amplifier's controls. The security cover is secured by a single hex-head
screw.

Simplified Gain Setting: The amplifier's R.I.P.S. feature also allows
for easy gain setup. Because the amplifier will always deliver the same amount
of power within its operational range of impedances and supply voltages, the
maximum, unclipped output is very predictable. This makes setting the gain level
of the amplifier via the input sensitivity control very simple. All you need is
Digital AC Voltmeter (142TK12V, sold separately) and a Test CD Disc (503CD104,
sold separately) with a sine-wave test-tone recorded at 0 dB reference level in
the frequency range to be amplified for that set of channels (50 Hz for
subwoofer channels, 1 kHz for a midrange application).

Input Mode: This
switch allows operation of all five amplifier channels with only one pair of
input signals (2ch); with independent front and rear input signal pairs
(4ch); or with discrete front, rear, and subwoofer signal pairs (6ch).

Input Voltage: This
switch allows you to choose between using a low-level input signal
(200mV-8V) or high-level input signal (200mv-2V).

High-Pass or Low-Pass Filter:
The HD900/5 has three individually
adjustable filter controls for the Front, Rear, and Subwoofer channels. The
Front and Rear filters are high-pass filters (attenuate low frequencies),
while the Subwoofer channel filter is a low-pass filter (attenuates high
frequencies). For each filter, you can select from a shallow (12dB/oct)
filter slope or a more aggressive (24dB/oct) slope.

Filter Frequency: This
control selects the frequency at which each high-pass or low-pass filter
begins to attenuate the signal and refers specifically the frequency at
which output has been attenuated by -3dB. You can select from 50-500Hz.

Infrasonic Filter (subwoofer only):
The Infrasonic Filter is a 24-dB/oct
high-pass filter, with a fixed cutoff frequency of 30Hz. This filter is
designed to conserve amplifier power and protect subwoofer systems, without
audibly degrading the subwoofer's bass output.

Connections

Power/Ground/Turn-On Plug: The amplifier features a Power/Ground/Turn-On plug which detaches from the
amplifier to make connecting your power, ground, and remote turn-on lead wires
more convenient. Once your connections are made the Power/Ground/Turn-On
connector simply plugs into the amplifier.

Power and Ground: The JL Audio amplifier's set-screw Power and Ground connections
found on the detachable Power/Ground/Turn-on plug are designed to accept 4 AWG power wire.
A hex-wrench is supplied for making connections.

Remote Turn-On: The JL Audio HD amplifier's set-screw
turn-on lead found on the Power/Ground/Turn-on plug will accept 18 to 12 AWG wire. A hex-wrench is supplied for making
connection.

Note: The Amplifier is not equipped with a fuse. An
external 60-amp AFS, AGU, or MAXI fuse (not included) must be installed on
the power wire. If a wiring kit is used which includes a fuse with a value
other than 60-amps, the original should be replaced with a 60-amp fuse

Speaker Output Plugs: The
amplifier features three Speaker Output plugs (Front/Rear/Sub) which detach from the amplifier for
easier speaker wire connection. Once your speaker wires are connected to these
plugs, they simply push into the amplifier. The front and rear speaker output plugs feature
four set-screw terminals, while the subwoofer speaker output plug features two
set-screw terminals. The HD900/5 amplifier's ten set-screw speaker
terminals found on the Speaker Output plugs will accept 16 to 12 AWG speaker wire. A hex-wrench is supplied for making
connections.

Preamp Inputs: The amplifier features three sets of differential-balanced
RCA jack inputs (Front/Rear/Sub). The amplifier features a
dedicated Input Sensitivity gain control for the front, rear, and subwoofer channels of the
amplifier. These controls are designed to match the input sensitivity of the
HD900/5 to the specific signal source that is feeding it. The amplifier's input level can be set independently for the front and rear channels to Low (200mV-2V RMS) when connecting the amplifier to a low-level preamp signal or set to High
(800mV-8V RMS) when connecting the amplifier to a high-level speaker signal.

Remote Level Control: The amplifier features a standard telephone
connector for adding an optional wired remote level control. With the addition
of the optional wired Remote Level Control (136HDRLC,
sold separately), you can control the volume
of one or both channel pairs of the HD900/5 form the front of your vehicle. This
is useful for subwoofer level control or even as a master volume control for
your system. If desired, multiple HD amplifiers can be controlled from a single
HD-RLC controller using a simple phone line splitter and multiple phone cables
(all sold separately).

Note: All inputs and outputs are located on the
rear
side of the amplifier to make installation of the amplifier simple and neat.

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to
find elsewhere. That's because we have our own in-house Product Research
team. They verify what’s in the box, check the owner's manual, and record
dimensions, features and specs. We stay on top of new products and technologies
to help people make informed choices.

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Review Guidelines for more information. We reserve the right (but are not
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Love the clarity, power and small size

I replaced a JL 500/5 and a 250/1 powering 4 satellites and 2 subs with this amp. I also moved down to one sub. I am very happy with the sound. the extra 150W to the rear speakers makes quite a difference. The amp seems a lot cleaner than the 500/5, but that could be the extra power to the rears. I set the front and sub crossovers to 80Hz, the rear crossovers to 120Hz, and adjusted the levels per the manual. I have not touched them since and have no plans to. I am very happy with the sound.

The modular plug-ins makes install much easier. Like the adjustments being on the opposite side, makes for easier access in my install.

Pros:Clean sound. Very small chassis for a 900W amp. Great power for a whole system amp. Easy adjustments. Clean and easy install.

Cons:Cons....cons.... um... Oh! The subsonic filter! Yes, i had to think to come up with something.
Why place it at 30hz?!?! (Yes, i know it's for ported boxes.) I would have like it adjustable, or selectable at 20Hz-30Hz. I have a ported enclosure, the HO110RG-W3v3, and it seems to not be as full with the filter on. I think 20Hz would have been perfect. This is a very minor gripe and really not an issue, still a 5 stars amp!

Powerful amp

This amp was a great purchase for what I was looking for. I have a 4 door wrangler and was upgrading the sound system when I ran into the problem of what kind of amp to get. I wanted to power my 4 speakers from the amp but also wanted a sub that had some power. This amp was able to power my C5 650s in the front and C3 650s in the sound bar with the TW5V2 in the stealth box. Perfect size to fit under the seat and more than enough power to keep me happy.

Very powerful little amp

Written By Nelson, South Fl. on Tuesday, May 21, 2013

Had too turn the gains down. Too loud for me. I was looking for a good small amp that fit under the seat. I have a very small car and battery but the amp doesn't seem to mind. Very few adjustments had to be made to get the type of sound quality I was looking for. Even the Eq. on the head unit is almost flat. Great job JL. And Thank You Crutchfield employees for putting up with all my questions. B.T.W. purchase the bass knob, it's a must!

Finally Size does not matter

Written By 2010Nitro, Woodbury, MN on Friday, May 03, 2013

I dont really know all the "tech mumbo jumbo". But here is my System, Im running the factory head unit (the 6" touch screen head unit) and this is running into a lower level 6 CH. line output(audiocontrol LC6I) into the JL HD900/5 This amp is powering two sets of Facal P165V15 components which are darn good speakers at $500 a pair. And also powering my 2 JLW3s subs. The shop that installed this said that they were impressed with the actual power this amp puts out when tuned correctly. Ive ran many different type of amp in the past. mostly a four CH. and a Mono amp for all of my systems, and my previous subs and speakers were a lot less then what i have now. I dont think I will ever run anything but a five ch JL . The awesome sound and power you get combined with the unreal small size of this amp makes it and easy choice.

Powerful, Small, Reliable

Very small footprint. Lots of power for its size. The HD900/5 is pushing front/rear Focal 130KR's with 10" sub. This is a perfect amp to power an entire system. Sound is clean. One thing I would like to point out (to my surprise) is the fact that there are a lot of YouTube videos pairing HD Series amplifiers with Focal components; event with the high dollar Utopia Be No.5. That is a bold statement regarding this amplifier. I recommend you use the proper metering equipment to set the gains/crossovers properly to be rewarded with clean, reliable and loud music. Applying sound deadening is like adding icing to the cake. In my garage,I tested the HD 900/5 by playing hip-hop for almost 100 minutes (power supply used) at 90% volume (only 90% because I was nervous about my component speakers). WOW! This amp did not shut down OR go into "protect" mode. Amplifier housing was warm/hot but that is to be expected after over 1.5 hours of playing. This amp is under rated and will certainly complement any 6x9, 6.5, 5.25 or component speaker set. Now I'm confident to open up my truck doors and play some music at BBQ's and family gatherings. There are higher priced amplifiers for the same or less amount of power but anything beyond the HD900/5 and you will start to pay more and get less...the point of diminishing returns.

Perfection

This small amp has the ability to power 4- JL Audio C2-690, 2- C2-075 tweeters and a W3V3 12 inch sub. Amazing sound in a small package. This single amp does the work of two amps in an exceptional manner. My car is a concert hall thanks to this amp and the components it powers.

Pros:Great sound, small package, One amp to power the entire system, stealth.

Huge sound, small package!

This is a great amp for the money. Chose this over the smaller XD line and I have no regrets. Power goes to bi-amping a Focal 3 way set in the front and two tens in the back. It sounds like nothing, which is what amps should sound like, completely transparent. Top audio competitors are using this line of amps and that says a lot. I bought the open box version and saved a hundred bucks. It came exactly the same as if it were new, not one bit of difference. Highly recommended!

Awesome Amp

Written By 2004wjmedic, Cullowhee, NC on Saturday, July 16, 2011

This is a great amplifier and my third JL Audio amp. I have the amp powering 4 JL Audio XR650 speakers C5 tweeters and a 10w7v2 subwoofer. I could not be happier with the power that this amp can pump out. It runs fairly cool and I have yet to be able to force it into a protect mode with long listening sessions at high volumes. Another plus is this amp is SMALL. I have it tucked away under the back seat in the factory location. If you buy this amp it, you will not be disappointed! Yes it is expensive but it is worth every penny.

True Power Ratings

Written By kevin, Minnesota on Monday, September 27, 2010

This amp gives you true rated power across a wide range of supply voltages, and in a compact chassis. The sound quality is superb, but again it always makes the rated power and stays cool. Paper specs do not do justice, this amp is worth every penny, it is that good.

Awesome

I have this amp pushing a 8w7. Everyone thinks i have 2 12's. it's also powering my to alpine component sets. It all sounds great..one of the cool things this amp does is it don't leave you with out music when it over heats it just turns the power down. so long as you turn your stereo down it will continue to sound great. I can't say enough about this amp it's simply awesome.

exceptional

This amp is seriously sick! i got a JL audio stealth box for my 07 mustang which has a 13w6 in it. I was using an amp that was supposedly pushing 850w rms to it but this thing is definitely louder and cleaner. I haven't hooked it up to my speakers yet, but i already know its gonna sound amazing. If you want a one amp solution to power your whole system, do yourself a favor and check this one out.

Great value and performance

After looking at Alpine and JL Audio digital amps for a while, JL finally came out with a perfect 5 channel that fit my needs. I swapped out two amps for one. And this one JL has great power. The sound is extremely clean, though the bass is not as loud as my old MTX mono amp that was rated the same at 1x500. But I didn't mind since I was trying to clean the bass to a more tight sound. I got new Focal polyglass 6.5 components, and pure heaven. Sound is amazaing. Focal and JL are top notch. Subs are 2 Infinity 12 inch Perfects combined to 2 ohms. I am still thinking about scaling down size to one 10 inch JL W6 and slamming that small sub hard. Amp gets hotter than expected. The size is unbelievably small. Get a great complete set-up in one small amp! Solid

Outstanding

Written By Goldfish, TX on Tuesday, October 13, 2009

I recently swapped my JL 300/2 and 500/1 for a HD600/4 and this HD900/5 and the difference is incredible. Sound quality is amazing and the space requirements are very minimal. The 10w3 woofer in a sealed box I have running off of the sub channel seems more precise and less "boomy" and I use the other channels bridged to a set of JL C5 components for the back doors. The sound quality on the back speakers is superb as well. This amp does seem to run a little bit warmer than the amps I had before, but I've had zero problems with either amp even after many continuous hours of loud volume levels. Overall, this amp and its 600/4 counterpart are worth every penny.